This invention relates to a plastic trial lens used for testing eyesight and the like of testees, an injection molded product for making the plastic trial lens, and a mold assembly for molding the injection molded product for the plastic trial lens.
A trial lenses exchanged method, that is one of subjective refraction tests, is adopted as one of prescriptions for glasses for selecting the most suitable lens for each user of glasses for some time. When the trial lenses exchanged method is conducted, a testee wears trial frames for trial lenses. Many kinds of trial lenses with various spherical diopters and astigmatic diopters and the like selected among a set of trial lenses are fitted in trial frames, thereby selecting the most suitable lens for each testee. A trial lens used in the trial lenses exchanged method has a grip portion on a periphery of a lens portion. By gripping the grip portion, the trial lens is set in and taken off from the trial frames.
A conventional trial lens is mainly made of glass. The trial lens is manufactured by attaching a holder ring member with a grip portion on the periphery of the lens cut (edge-filed) into the fixed size (Japanese Utility Model Laid-open No. Hei 4-22902). Some of conventional trial lenses are plastic, but the manufacturing process after cutting is the same as that of glass trial lenses.
Besides manufacturing lenses, the conventional trial lens manufacture requires the process of manufacturing members for grip portions with different materials from lenses and attaching the members on lenses, which takes a lot of time and labor.
Members for grip portions are made of metal in view of durability and easy operation, which causes a disadvantage that a trial lens is heavy as a whole. In complicated prescriptions for glasses for astigmatism, glasses for both far vision and near vision and the like, trial tests are conducted by setting more than one trial lenses one on another in trial frames so that ears and a nose of a testee get a heavy weight, which causes another disadvantage that trial frames are easy to slip off. A diameter of the trial lens is short so that after-processing such as edge-filing and holder ring attaching is difficult. The grip portion is disposed at the fixed angle, for example, at the upper right or at the upper left of the lens in consideration of setting work in trial frames. In a trial lens with a difference between the top and the bottom and between the right and the left, such as a progressive multifocal lens and a lens with astigmatism, when a holder ring with a grip portion is attached on the periphery of the trial lens, precise positioning of the above fixed angle concerning the grip portion is required in accordance with an optical layout in the design of the lens about an optical center position and the like, which makes the attaching process of the holder ring difficult in the trial lens with a short diameter. Moreover, when the holder ring with the grip portion is caulked too strongly on the periphery of the lens, in a plastic lens this situation causes an optical surface to deform, which brings about optical distortion and the like.
An object of the present invention is to provide a plastic trial lens, in which the process of manufacturing a member for a grip portion with different materials from a lens and attaching the member on the lens is omitted, the whole trial lens is more light-weight and the precise layout of the grip portion in relation to the lens portion is obtained, and an injection molded product to make the plastic trial lens, and moreover a mold assembly to mold the injection molded product.
A plastic trial lens according to the present invention is provided with a lens portion and a grip portion integrally formed on a periphery of the lens being gripped when the lens portion is set in trial frames for trial lenses, the grip portion being molded simultaneously with the lens portion.
The trial lens according to the present invention is plastic, in which the grip portion is integrally molded with the lens portion. The lens portion and the grip portion are molded out of the same synthetic resin, the grip portion being molded simultaneously with the lens portion, which omits the process of attaching a member for the grip portion on the lens portion. The grip portion is formed out of the same synthetic resin as the lens portion so that the whole trial lens is lightweight. The grip portion is integrally molded with the lens portion after being positioned in a mold assembly so as to be formed in the fixed position of the lens portion, and hence the grip portion is disposed in relation to the lens portion in the fixed position accurately laid out.
An injection molding method, an injection compression molding method or a casting method (cast molding method) can be adopted to manufacture the above-described plastic trial lens in which the lens portion and the grip portion are integrally molded.
However, the casting method uses a thermosetting resin (diethylene glycol bisuallyl carbonate is typical) for materials. The polymerization shrinkage percentage of the thermosetting resin is as large as about 14 percent. Therefore, the difference between a lens shape in design and a real mold transfer shape is large so that extremely high manufacturing technology is required to make mold transfer precision of a molded product attain the high precision required for the trial lens. In addition, molding a plastic lens by means of the casting method requires a molding time of from 12 to 24 hours to precisely control polymerization of the resin for the materials. As a result, one cycle of molding time becomes long, thus making mass-production of trial lenses costly. For the reasons stated above, it is preferable that the plastic trial lens is molded by means of the injection molding method or the injection compression molding method in which any disadvantage as described above does not occur.
When the plastic trial lens is molded by means of the injection molding method or the injection compression molding method, the thermoplastic resin used is a material such as PMMA (polymethyl methacrylate) system resin or PC (polycarbonate) system resin.
A holder ring can be attached on the periphery of the lens portion of the plastic trial lens, but it is preferable that a edge portion instead of the holder ring is integrally provided on the periphery of the lens portion, the edge portion being molded simultaneously with the lens portion.
Using the edge portion instead of the holder portion helps the trial lens to be more lightweight and omits a member for the holder ring. In addition, the process that the holder ring is caulked on the periphery of the lens portion is unnecessary, which secures high optical precision of the lens portion.
The plastic trial lens according to the present invention can be a progressive multifocal lens with a portion for far vision, a portion for near vision and a progressive portion between the portion for far vision and the portion for near vision or a lens with astigmatism. The present invention is applicable to both a single vision lens and a multifocal lens which has a portion for near vision and a portion for far vision but no progressive portion.
When the trial lens is a progressive multifocal lens, it is preferable that the lens is provided with a mark indicating a direction of a horizontal datum line and a grip portion shifting to the right or the left from the center between the right portion and the left portion of the lens portion on the periphery of the lens portion according to the lens for a right eye or for a left eye.
Thus, the distinction between a lens for a right eye and a left eye in each progressive multifocal trial lens and the horizontal direction are clearly known with the position of the grip portion and the mark. As a result, while distinguishing the trial lens for a right eye from that for a left eye, the position of the revolving direction of the round shaped lens portion as a whole in each trial lens is accurately fixed so that the trial lens can be fitted in the trial frames in accurate position. Also, a diopter measuring position in the portions for far vision and for near vision in the lens portion or a layout of optical center can be easily known with the grip portion and the mark.
The mark for indicating a horizontal datum line can be provided after the lens is molded by means of injection molding and also molded simultaneously with the lens portion and the grip portion. If the mark is molded simultaneously as described above, a manufacturing process is cut, thus improving manufacturing efficiency.
When the mark is molded simultaneously with the lens portion and the grip portion, the mark is formed as a dented portion or a projected portion in the lens portion. However, it is preferable that the mark is not a projected portion but a dented portion. If the mark is a projected portion, the projected portion becomes a hindrance, for example, it catches in the trial frames when the trial lens is fitted in the trial frames. The dented portion as the mark can be dented from one surface of the lens portion and also cut deep in an inside diametrical direction of the lens portion. Moreover, it is possible to combine the above two ways.
Many sorts of diopters are provided in the aforesaid progressive multifocal lens. The present invention is applicable to trial lenses with various diopters, to take an example, a lens with 0.00 diopter in a portion for far vision in which the dipoter for near vision is fixed only in a portion for near vision. This type of trial lens can be set in the trial frames with a single vision trial lens for far vision or near vision one on another.
An injection molded product for making the plastic trial lens according to the present invention is provided with a lens portion, a liquid guided and collected area integrally formed on a periphery of the lens portion in which coating liquid flowing down on surfaces of the lens portion is guided and collected when the lens is dipped into and pulled up from the coating liquid, and a grip portion gripped when the lens portion is set in the trial frames after the liquid guided and collected area is removed. The liquid guided and collected area and the grip portion are molded simultaneously with the lens portion.
Dipping process that the injection molded product is dipped into the coating liquid is conducted to form a coating film made out of the hard coat liquid on surfaces of the trial lens. The hard coating film improves abrasion-resistance and durability of the trial lens.
When the injection molded product with the lens portion is dipped into and pulled up from the coating liquid, the coating liquid flows down on the surfaces of the lens portion, while a coating liquid collected portion is formed at the bottom of the lens portion. This causes a difference in thickness of coating film between a part nearby and a part far from the liquid collected portion, thus changing a curvature of a lens surface, which sometimes affects the lens diopter. As a result, serious disadvantage may occur from the viewpoint of the precision of trial lenses.
In the present invention, when the lens portion is molded by means of the injection molding method or the injection compression molding method, the liquid guided and collected area as well as the grip portion is molded at the same time on the periphery of the lens portion. The liquid guided and collected area is formed to guide the coating liquid flowing down on the surfaces of lens portion when the injection molded product is dipped into and pulled up from the coating liquid, and to collect the remaining liquid without dripping. Consequently, a liquid collected portion is formed in the liquid guided and collected area so as to ease the effects on the lens portion by the liquid collected portion, which virtually assures the uniformity in thickness of coating film.
When the liquid guided and collected area having the above-described effects is formed in the injection molded product for the trial lens, in the present invention the liquid guided and collected area as well as the grip portion is simultaneously molded on the periphery of the lens portion, thereby facilitating the molding process.
The shape of liquid guided and collected area is optional if the coating liquid flowing down on the surfaces of the lens portion can be guided and the remaining liquid without dripping down can be collected in the area when the injection molded product is dipped in and pulled up from the coating liquid, for example, a bar shape extending in an outside diametrical direction of the lens portion (downward when pulled up from the coating liquid) or a fan shape with a small projection in an outside diametrical direction and two long sides extending in a circumferential direction is available.
The liquid guided and collected area is, however, removed when the lens portion is set in the trial frames by gripping the grip portion after the trial lens is finished. In order to facilitate the removing process and keep the liquid collected portion formed of the coating liquid flowing down on the surfaces of the lens portion away from the lens portion, the liquid guided and collected area is preferably shaped into a bar extending in an outside diametrical direction.
The grip portion and the liquid guided and collected area integrally molded on the periphery of the lens portion can be formed in an optional positional relationship, but preferably the grip portion and the liquid guided and collected area are formed opposite each other on the periphery of the lens portion.
As a result, when the injection molded product is dipped into the coating liquid, by placing the liquid collected and guided area downward and the grip portion upward the injection molded product is dipped into the coating liquid by supporting the grip portion with a supporting utensil such as a clip. Moreover, when the injection molded product is pulled up from the coating liquid, the coating liquid collected portion is formed in the liquid guided and collected area that is disposed downward, thereby forming the coating film of uniform thickness on the surfaces of the lens portion as predetermined.
In the above case, the grip portion is used to be gripped when the lens portion is set in the trial frames and also used as a supported portion to be supported with the supporting utensil when the injection molded product with the lens portion is dipped into the coating liquid.
In the injection molded product, one lens portion can be formed or more than one lens portions can be formed in two-dimensional or three-dimensional positional relationship, that is, the injection molded product can make one lens or more than one lenses.
In the injection molded product for making more than one lenses, preferably more than one lens portion are coupled to each other by means of a coupling portion, the coupling portion being provided with a supported portion supported when the lens portions are dipped into the coating liquid, and the liquid guided and collected area is formed on an opposite side to the supported portion on a periphery of each lens portion.
Consequently, each lens portion is dipped into the coating liquid by supporting the supported portion disposed upward with the supporting utensil. Thus all lens portions are dipped into the coating liquid at the same time and the liquid collected portion is formed in each liquid guided and collected area, since each liquid guided and collected area is disposed downward when each lens portion is pulled up from the coating liquid.
In the above-described injection molded product for making the trial lens, the grip portion and the liquid guided and collected area are separately formed. However, an injection molded product with a portion serving both as a grip portion and a liquid guided and collected area can be manufactured.
In other words, this type of injection molded product for the trial lens is provided with a lens portion and a grip portion molded simultaneously with the lens portion on the periphery of the lens portion being gripped when the lens portion is set in trial frames. Since the grip portion is disposed downward when the lens portion is dipped into the coating liquid, the grip portion also serves as a liquid guided and collected area in which the coating liquid flowing down on surfaces of the lens portion is guided and collected when the lens portion is pulled up from the coating liquid.
The injection molded product for the trial lens can be an injection molded product for a progressive multifocal lens with a portion for far vision, a portion for near vision and a progressive portion between the portion for far vision and the portion for near vision or an injection molded product for a lens with astigmatism. In addition, the injection molded product is applicable to both a single vision lens and a multifocal lens which has a portion for far vision and a portion for near vision but no progressive portion.
When a progressive multifocal lens is obtained from the injection molded product, as described above the progressive multifocal lens has 0.00 diopter in a portion for far vision in which the dipoter for near vision is fixed only in a portion for near vision. This type of trial lens can be set in the trial frames with a single vision trial lens for far vision or near vision one on another.
When the lens portion in the injection molded product is a progressive multifocal lens portion with a portion for far vision, a portion for near vision and a progressive portion between the portion for far vision and the portion for near vision, the grip portion is preferably formed on the periphery of the side of the portion for far vision out of both sides of portions for far vision and near vision in the lens portion. When the grip portion is formed on the periphery of the side of the portion for near vision in the lens portion, a groove depending on a sectional shape of the portion for near vision is formed in a boundary between an edge portion and the portion for near vision in the lens portion so that the coating liquid is likely to be collected in the groove. When the grip portion is formed on the periphery of the side of the portion for far vision in the lens portion, the above-mentioned disadvantage does not occur, thus securing high optical precision of the lens portion.
The injection molded product for the trial lens, in which the grip portion serves as the liquid guided and collected area, is provided with a supported portion supported with a supporting utensil when the injection molded product is dipped into the coating liquid. The supported portion can be formed in an optional positional relationship to the grip portion, but preferably the supported portion is formed on the opposite side to the grip portion on the periphery of the lens portion.
As a result, when the injection molded product is dipped into the coating liquid, by placing the grip portion downward and the supported portion upward the injection molded product is dipped into the coating liquid by supporting the supported portion with a supporting utensil such as a clip. Moreover, when the injection molded product is pulled up from the coating liquid, the coating liquid collected portion is formed in the grip portion that is disposed downward, thereby forming the coating film of uniform thickness on the surfaces of the lens portion as predetermined.
Preferably the supported portion is molded simultaneously with the lens portion and the grip portion, which can cut a manufacturing process.
The shape of supported portion is optional if it can be surely supported with the supporting utensil, for example, a bar shape extending in an outside diametrical direction of the lens portion or a fan shape with a small projection in an outside diametrical direction and two long sides extending in a circumferential direction is available.
The supported portion is, however, removed when the lens portion is set in the trial frames by gripping the grip portion after the trial lens is finished. In order to facilitate the removing process, the supported portion is preferably shaped into a bar extending in an outside diametrical direction of the lens portion and having a small connecting area with the lens portion.
A mold assembly for molding the injection molded product for the plastic trial lens according to the present invention is provided with two molds to be parted, a pair of inserts disposed in each of the molds which form a cavity for molding the plastic trial lens by molten synthetic resin filled when the molds are mold-closed. The cavity includes a lens molded portion to mold the lens portion of the trial lens and a grip molded portion to mold the grip portion on the periphery of the lens portion being gripped when the lens portion is set in trial frames.
In the mold assembly, the cavity between a pair of the inserts includes the lens molded portion and the grip molded portion. Therefore, when the molten synthetic resin is filled in the cavity, the lens portion and the grip portion of the trial lens are molded at the same time.
Two molds to be parted in the mold assembly consist of a top mold and a bottom mold or a right mold and a left mold. In other words, the mold assembly can be structured both vertically and horizontally.
The injection molded product for the trial lens molded in the mold assembly can be the injection molded product for a progressive multifocal lens with a portion for far vision, a portion for near vision and a progressive portion between the portion for far vision and the portion for near vision or the injection molded product for a lens with astigmatism. In addition, the injection molded product is applicable to both a single vision lens and a multifocal lens which has a portion for far vision and a portion for near vision but no progressive portion.
The mold assembly can be used for molding more than one progressive multifocal trial lenses with different additions. In this case, it is preferable that the mold assembly is provided with more than one set of a pair of inserts, the lens portion molded between more than one set of the inserts is a progressive multifocal lens portion with a portion for far vision, a portion for near vision and a progressive portion between the portions for far vision and for near vision, a spacer for adjusting the thickness of the lens is disposed on the back side of one insert out of a pair of the inserts opposite each other, and more than one spacer having a different thickness are provided in more than one set of the inserts so that more than one progressive multifocal lenses with different additions are molded by means of the spacers having different thicknesses.
A concave surface side of the progressive multifocal lens portion that is a meniscus lens is a spherical surface with a fixed curvature. By a curvature of a convex surface side which is an aspheric surface, the shape of the lens surface and the diopter change. As the addition is enlarged, the thickness of the center of the lens becomes large and the volume of the lens increases. When more than one lens portion with different additions are molded in the mold assembly at the same time, a large difference in volume among the lens portions affects molding conditions, which makes it difficult to secure high optical precision for all the lens portions. In the present invention, to virtually fix the volume of each lens portion regardless of the addition, first an intermediate addition is set, then the lens thickness of the lens portion with the intermediate addition is found and this thickness becomes a standard against which the thickness of each of other lens portions with different additions is redesigned. In a lens portion with an addition smaller than the above intermediate value the volume of the lens is increased, while in a lens portion with an addition larger than the above intermediate value the volume of the lens is decreased.
With regard to the spacer, spacers with a thickness larger than and smaller than the spacer with the intermediate thickness are made so as to obtain lens portions with additions larger than and smaller than the intermediate addition. The spacers having a different thickness are disposed on the back of the insert on one side out of more than one set of the inserts so that a difference in capacity (volume of the lens portion) among more than one cavity to mold more than one sort of progressive multifocal lens portion with different additions is adjusted. As a result, molding conditions in each trial lens portion formed by filling the molten synthetic resin in the cavity become almost uniform, which raises mold transfer efficiency in each cavity and ensures high optical precision.
In the mold assembly according to the present invention, a back insert can be disposed on the back side of one of a pair of the inserts and a position of a molded surface of the lens portion in one insert in relation to the other insert can be established by the length of the back insert.
The position of the molded surface of the lens portion in one insert in relation to the other insert is established by the length of the back insert. Therefore, only a molded surface of the lens portion is required for high-precision finishing in one insert, which can facilitate the work of manufacturing and processing the above one insert.
The cavity formed between a pair of the inserts can include an edge molded portion to mold the edge portion serving as the holder ring on the periphery of the lens portion.
In this case, in the plastic trial lens obtained from the injection molded product the holder ring does not need to be attached on the periphery of the lens portion, thus simplifying manufacturing process of the trial lens.
A grip molded portion to mold the grip portion on the periphery of the lens portion can be formed in relation to a lens molded portion to mold the lens portion in an optional circumferential directional position. However, preferably the grip molded portion is formed between a gate from which molten synthetic resin flows into the cavity and the lens molded portion in the cavity.
When the molten synthetic resin flows into the cavity from the gate, the molten synthetic resin is filled in the lens molded portion through the grip molded portion so that distortion by filling the molten synthetic resin is easy to break out in a portion of resin near the gate, but the distortion occurs in the portion of resin filled in the grip molded portion, which prevents distortion from breaking out in a portion of resin filled in the lens molded portion, thus securing high precision of the lens.
A pair of the inserts to form the cavity can be formed with each member disposed in each mold to be parted, but preferably a pair of the inserts respectively include an inner insert member to mold the lens portion and an outer insert member disposed on the outside of the inner insert member to mold the grip portion.
Consequently, when more than one sort of trial lenses with different additions in the lens portions, which are provided with the grip portions integrally on the periphery of the lens portions, are manufactured, only the inner inserts are exchanged and the outer insert can be used in common for more than one sort of the trial lenses.
Materials for members composing the mold assembly can be metal, ceramic or glass, and in addition, the above different kinds of materials can be used for more than one member.